Recently our research has focused on three neuromuscular diseases: autosomal recessive spinal muscular atrophy (SMA) due to deficiency of the protein SMN, spinal and bulbar muscular atrophy (SBMA) due to polyglutamine expansion in the androgen receptor, and amyotrophic lateral sclerosis type 4 (ALS4) due to mutation in senataxin. Specific research accomplishments include the following: (1) Polyglutamine expansion in androgen receptor (AR) is responsible for SBMA and leads to selective loss of lower motor neurons. We evaluated the effect of polyglutamine length on AR function in Xenopus oocytes. This allowed us to correlate the nuclear AR concentration to its capacity for specific DNA binding and transcription activation in vivo. AR variants with polyglutamine tracts containing either 25 or 64 residues were expressed in Xenopus oocytes by cytoplasmic injection of the corresponding mRNAs. The intranuclear AR concentration was monitored in isolated nuclei and related to specific DNA binding as well as transcriptional induction from the hormone response element in the mouse mammary tumor virus (MMTV) promoter. The expanded AR with 64 glutamines had increased capacity for specific DNA binding and a reduced capacity for transcriptional induction as related to its DNA binding activity. (2) In SBMA, as in other polyglutamine diseases, a toxic gain of function in the mutant protein is an important factor in the disease mechanism; therefore, therapies aimed at reducing the mutant protein hold promise as an effective treatment strategy. Gene silencing by RNA interference has recently evolved as a viable therapeutic option. We evaluated a microRNA (miRNA) approach to achieve AR repression. We identified and characterized microRNA-298 (miR-298), which binds to the 3'-untranslated region of the human AR transcript, down-regulates AR mRNA and protein levels and counteracts AR toxicity in vitro. Intravenous delivery of miR-298 via adeno-associated virus serotype 9 vector resulted in efficient transduction of muscle and spinal cord and amelioration of the disease phenotype in SBMA mice. Our findings support the development of miRNAs as a therapeutic strategy for SBMA and other polyglutamine diseases. (3) It has been suggested that proteins with expanded polyglutamine tracts impair ubiquitin-dependent proteolysis due to their propensity to aggregate, but recent studies indicate that the overall activity of the ubiquitin-proteasome system is preserved in SBMA models. We found that AR selectively interferes with the function of the ubiquitin ligase anaphase-promoting complex/cyclosome (APC/C), which, together with its substrate adaptor Cdh1, is critical for cell cycle arrest and neuronal architecture. We showed that both wild-type and mutant AR physically interact with the APC/CCdh1 complex in a ligand-dependent fashion without being targeted for proteasomal degradation. Inhibition of APC/CCdh1 by mutant but not wild-type AR in PC12 cells resulted in enhanced neurite outgrowth which is typically followed by rapid neurite retraction and mitotic entry. Our data indicate a role of AR in neuronal differentiation through regulation of APC/CCdh1 and suggest abnormal cell cycle reactivation as a pathogenic mechanism in SBMA. (4) We characterized a novel curcumin analog, ASC-JM17, as an activator of central pathways controlling protein folding, degradation, and oxidative stress resistance. ASC-JM17 acts on Nrf1, Nrf2, and Hsf1, to increase the expression of proteasome subunits, antioxidant enzymes, and molecular chaperones. We showed that ASC-JM17 ameliorates toxicity of the mutant androgen receptor (AR) responsible for SBMA in cell, fly, and mouse models. Knockdown of the Drosophila Nrf1 and Nrf2 ortholog CncC, but not Hsf1, blocked the protective effect of ASC-JM17 on mutant AR-induced eye degeneration in flies. Our observations indicate that activation of the Nrf1/Nrf2 pathway is a viable option for pharmacological intervention in SBMA and potentially other polyglutamine diseases. (5) The development of therapeutics for neurological disorders is constrained by limited access to the central nervous system (CNS). AT-binding cassette (ABC) transporters, particularly P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), are expressed on the luminal surface of capillaries in the CNS and transport drugs out of the endothelium back into the blood against the concentration gradient. SMN protein, which is deficient in SMA, is a target of the ubiquitin proteasome system. Inhibiting the proteasome in a rodent model of SMA with bortezomib increases SMN protein levels in peripheral tissues but not the CNS, because bortezomib has poor CNS penetrance. We sought to determine if we could inhibit SMN degradation in the CNS of SMA mice with a combination of bortezomib and the ABC transporter inhibitor tariquidar. In cultured cells we showed that bortezomib is a substrate of P-gp. Mass spectrometry analysis demonstrated that intraperitoneal co-administration of tariquidar increased the CNS penetrance of bortezomib, and reduced proteasome activity in the brain and spinal cord. This correlated with increased SMN protein levels and improved survival and motor function of SMA mice. These findings show that CNS penetrance of treatment for this neurological disorder can be improved by inhibiting drug efflux at the blood-brain barrier. (6) Numerous strategies using gene and cell therapy are being developed for the treatment of neurodegenerative disorders. Many of these strategies utilize constitutive expression of therapeutic transgenic proteins. Although functional in animal models of disease, this method is less likely to provide adequate flexibility for regulating the expression of the therapeutic proteins in humans. We described the modification and production of a mifepristone-inducible vector system for regulated expression of transgenes within the central nervous system. Mifepristones ability to cross the blood-brain barrier makes it an especially attractive inducible ligand for transgene expression in the brain and spinal cord. Our inducible system used a lentivirus-based vector platform for the ex vivo production of mifepristone-inducible murine neural progenitor cells that express our transgenes of interest. These cells were processed through a series of selection steps to ensure the cells exhibited appropriate transgene expression in a dose-dependent and temporally controlled manner with minimal background activity. Inducible cells were then transplanted into the brains of rodents, where they exhibited appropriate mifepristone-inducible expression. These studies detail a strategy for regulated expression in the CNS for the potential development of an efficient and safe method for future gene therapies for neurological disorders.